According to study results published in BMJ, lowering carbohydrate consumption increases energy expenditure during weight loss maintenance, which might increase the odds of successful obesity treatment.
To determine how diets varying in carbohydrate-to-fat ratio affect total energy expenditure, researchers randomly assigned 164 adults with a body mass index of ≥25 kg/m2 to a 20-week test diet. The study diets varied in carbohydrate content; researchers assigned 54 participants to a high-carbohydrate diet (60% of total energy), 53 to a moderate-carbohydrate diet (40% of total energy), and 57 to a low-carbohydrate diet (20% of total energy).
In the intention-to-treat analysis, total energy expenditure was found to differ significantly by diet (P =.002), with a linear trend of 52 kcal/day per 10% decrease in carbohydrate contribution to total energy. Compared with the high-carbohydrate group, participants in the moderate group expended 91 more kcal/day, and participants in the low group expended 209 more kcal/day.
The investigators also conducted a per protocol analysis, which included a subset of participants who maintained weight loss within 2 kg of baseline weight. In this analysis (n = 120; P <.001), the researchers discovered differences of 131 kcal/day in the moderate-carbohydrate group and 278 kcal/day in the low-carbohydrate group. Effects of alternate carbohydrate levels in diet were greatest in individuals who had high insulin secretion before weight loss. For participants in the highest third of pre-weight-loss insulin secretion, there were significant differences between the low- vs high-carbohydrate diets: 308 more kcal/day in the intention-to-treat analysis low-carbohydrate group (P =.004), and 478 more kcal/day in the per protocol analysis low-carbohydrate group (P <.001).
In addition, ghrelin levels were significantly lower in the low-carbohydrate group than in the high-carbohydrate group (P =.02 for both analyses), and the same was true for leptin levels (P =.07 for intention-to-treat, P =.009 for per protocol).
Several limitations were noted for this study, including potential measurement error, noncompliance, and generalizability.
Despite such limitations, the researchers said their results demonstrate that “dietary quality can affect energy expenditure independently of body weight, a phenomenon that could be key to obesity treatment.”
Ebbeling CB, Feldman HA, Klein GL, et al. Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial. BMJ. 2018;363:k4583.